This invention is in the field of plant molecular biology. More specifically, this invention pertains to nucleic acid fragments encoding sugar transport proteins in plants and seeds.
Sugar is one form of carbohydrate produced in photosynthesizing cells in most higher plants and is the main form of transported carbon in most annual field crops such as corn, rice, soybeans and wheat. As such its movement and concentration across various plant membranes is critical to plant growth and development. In addition sugar is the main form of carbon that moves into developing seeds of soybeans, rice, corn and wheat. This movement and concentration is accomplished by the action of carrier proteins that act to transport sugar against a concentration gradient often by coupling sugar movement to the opposite vectoral movement of a proton. Specific sugar carrier proteins from these crop plants could be manipulated in efforts to control carbon flux and the timing and extent of sugar transport phenomena (e.g., grain fill duration) that are important factors in crop yield and quality. Accordingly, the availability of nucleic acid sequences encoding all or a portion of sugar transport proteins would facilitate studies to better understand carbon flux and sugar transport in plants, provide genetic tools for the manipulation of sugar transport, and provide a means to control carbohydrate transport and distribution in plant cells.
The instant invention relates to isolated nucleic acid fragments encoding sugar transport proteins. Specifically, this invention concerns an isolated nucleic acid fragment encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein. In addition, this invention relates to a nucleic acid fragment that is complementary to the nucleic acid fragment encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein.
An additional embodiment of the instant invention pertains to a polypeptide encoding all or a substantial portion of a sugar transport protein selected from the group consisting of Arabidopsis thaliana-like sugar transport protein and Beta vulgaris-like sugar transport protein.
In another embodiment, the instant invention relates to a chimeric gene encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein, or to a chimeric gene that comprises a nucleic acid fragment that is complementary to a nucleic acid fragment encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein, operably linked to suitable regulatory sequences, wherein expression of the chimeric gene results in production of levels of the encoded protein in a transformed host cell that is altered (i.e., increased or decreased) from the level produced in an untransformed host cell.
In a further embodiment, the instant invention concerns a transformed host cell comprising in its genome a chimeric gene encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein, operably linked to suitable regulatory sequences. Expression of the chimeric gene results in production of altered levels of the encoded protein in the transformed host cell. The transformed host cell can be of eukaryotic or prokaryotic origin, and include cells derived from higher plants and microorganisms. The invention also includes transformed plants that arise from transformed host cells of higher plants, and seeds derived from such transformed plants.
An additional embodiment of the instant invention concerns a method of altering the level of expression of an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein in a transformed host cell comprising: a) transforming a host cell with a chimeric gene comprising a nucleic acid fragment encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein; and b) growing the transformed host cell under conditions that are suitable for expression of the chimeric gene wherein expression of the chimeric gene results in production of altered levels of Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein in the transformed host cell.
An additional embodiment of the instant invention concerns a method for obtaining a nucleic acid fragment encoding all or a substantial portion of an amino acid sequence encoding an Arabidopsis thaliana-like sugar transport protein or Beta vulgaris-like sugar transport protein.